That's a GOOD new to read!It would be nirvana also to federate with GNU Social/Mastodon. Then we can ask most of the people fed up by FB/G+/twitter censorship to move to free-as-in-freedom alternatives.The question then will be: will the existing server be able to bear the load?

All updated mastodon instances use activitypub for federation between themselves and only use ostatus when federating to gnusocial instances. I'm not sure of the version where this switch happened, but instances not updated to that version would still use ostatus solely.

OStatus is a decentralized social networking protocol made up of several other protocols (Atom feeds, Activity Streams, PubSubHubbub, Salmon, and WebFinger) GNU Social and Mastodon are two server software applications that implement OStatus pump.io API is an interface to the pump.io server software (Activity Streams, OAuth, Web Host Metadata) identi.ca is a pump.io instance (not accessible right now), GNU MediaGoblin is a server application that currently uses a pump-like API ActivityPub is a proposed decentralized social networking protocol GNU MediaGoblin is a server application that will likely implement ActivityPub

How do these protocols interoperate? Does ActivityPub completely replace OStatus, or only the Activity Streams component?

I've been hoping for some interaction with ActivityPub, but at least since they use PostgreSQL at the very least the database itself can store JSON in the same format ActivityPub sendsIt's just a matter of someone coding it.